The present invention relates to an ion source to be used for ion beam etching, ion beam sputtering and the like, and to an ion beam device provided with the ion source.
In an ion beam device, ions are derived from plasma generated in the ion source and the derived ions are used for various processes. For example, in an ion beam etching device, the derived ions are irradiated on a base plate for etching. In an ion beam sputtering device, a target is subjected to sputtering by the derived ions.
Incidentally, when the base plate or target is made of an insulation material or covered with an insulation material, positive charge of the irradiated ions is accumulated on the insulation material, so that the base plate or the target is positively charged due to the charge build-up. Therefore, it is difficult to irradiate the ions on the base plate or the target due to an electric field of the accumulated positive charge.
Heretofore, as a method for preventing such a charge build-up, there has been a method wherein a metal heater such as a tungsten filament is disposed in a path of the ion beams between an ion source and an object to be processed (base plate or target). When the heater is heated to a high temperature, the heater generates thermal electrons to neutralize the accumulated positive charge. Also, there has been a method wherein a plasma source is provided separately from an ion source between the ion source and an object to be processed. The plasma source generates electrons to neutralize the positive charge accumulated on the object to be processed, as disclosed in Japanese Patent Publication (Kokai) No. 2003-31175.
In the method using the metal heater, the metal heater is exposed to the ions so that the metal heater is subjected to sputtering, resulting in pollution. In a case of the reactive ion beam etching (RIBE), a reaction between the metal heater and the process gas becomes a problem. In the method using the separate plasma source, the plasma is generated through DC discharge, RF discharge, ECR using a microwave, and the like. In any case, it is necessary to separately provide a device for exciting the plasma, thereby making an adjustment thereof difficult and increasing a cost of the device.
In view of the above problems, the present invention has been made, and an object of the invention is to provide an ion source in which it is possible to prevent the charge build-up of a target by using electrons in plasma, and an ion beam device provided with the ion source.
Further objects and advantages of the invention will be apparent from the following description of the invention.